Tomosynthesis reconstructs structures existing within an imaged object from a set of projection radiographs. These structures include, for example in medical applications, anatomical structures such as organs, blood vessels, and bones. In computed tomography both an x-ray source (which is also referred to as a tube) and a detector move on a circular trajectory around a common axis and a very high number of projection radiographs (or images) is acquired. That is, in computed tomography, the x-ray source and detector typically describe either a full circle around the object or a half-circle for each, x-ray source and detector. In conventional motion tomography, the x-ray source describes an arc essentially on one side of the object and the detector (or film) describes a corresponding arc (in the opposite direction) on the opposite side of the object, while one horizontal slice through the object remains in focus. In contrast, in tomosynthesis, relatively few radiographs are acquired for varying x-ray source positions. Tomosynthesis, then, is a system and method that acquires a plurality of projection radiographs, where the x-ray source assumes positions that are essentially on one side of the object, while the detector (or film) assumes positions on the opposite side of the object.
A digital tomosynthesis system comprises an x-ray source and a digital detector which are connected to each other by an appropriate mechanical structure. Generally, a number of 2-dimensional projection radiographs of a stationary imaged object is acquired at different positions of the x-ray source relative to the imaged object, and from the data sets corresponding to the 2-dimensional projection radiographs, the 3-dimensional structure of the imaged object is reconstructed.
Conventional tomosynthesis systems and methods are not optimally suited to reconstruct an object from a limited number of digital radiographic projection images which are acquired with the x-ray source being located at a constant height above a which are acquired with the x-ray source being located at a constant height above a plane containing the detector. Moreover, the employed reconstruction techniques usually require a data interpolation step before the actual reconstruction is carried out. This interpolation step brings with it an irreversible loss in resolution, i.e., fine details (small structures) are lost before the 3D reconstruction even begins.